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[+my non-arm account]
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<div class="">Hi,</div>
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<div class="">I believe I have a testcase for that too. The key is the word “conflicting” - we can have multiple edges from the same predecessor, but to be well formed all phi values for those arcs must be the same. The verifier checks this, if I recall.</div>
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<div class="">I’ll make sure there’s a testcase at least for the full expected behaviour (this pass is off by default at the moment so there’s no panic about trunk miscompiling).</div>
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<div class="">James</div>
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<div class="">On 25 May 2017, at 16:11, Daniel Berlin <<a href="mailto:dberlin@dberlin.org" class="">dberlin@dberlin.org</a>> wrote:</div>
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<div dir="ltr" class="">(That comment applies mostly to newgvn).
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<div class="">In your case, i believe the code is just wrong:<br class="">
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<div class="">/ This assumes the PHI is already well-formed and there aren't conflicting</div>
<div class=""> // incoming values for the same block.</div>
<div class=""> for (auto *B : Blocks)</div>
<div class=""> Values.push_back(PN->getIncomingValueForBlock(B))</div>
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<div class="">It's 100% completely and definitely possible for a phi to have two values incoming from the same block, actually, regardless of whether it's a self block or not.</div>
<div class="">This happens using switch statements.</div>
<div class="">I believe we even have some testcases in newgvn for multiple edges from same incoming block.</div>
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<div class="">So yeah, you have to handle them here.</div>
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<div class="gmail_quote">On Thu, May 25, 2017 at 8:08 AM, Daniel Berlin <span dir="ltr" class="">
<<a href="mailto:dberlin@dberlin.org" target="_blank" class="">dberlin@dberlin.org</a>></span> wrote:<br class="">
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</span><span class="">dberlin wrote:<br class="">
> I'm curious why you think you need stable sort here as opposed to regular<br class="">
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</span>I don't. Changed.<br class="">
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<div class="">(i'm offsite today, but someone should test this in newgvn too if i'm right).</div>
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<div class="">Do we allow switch statements with multiple edges to ourself?<br class="">
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ie</div>
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switch <whatever> [</div>
<div class="">i32 0 : label bb1</div>
<div class="">i32 1: label bb1 ]</div>
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<div class="">(which, after propagation, could cause a phi with different operands and the same incoming blocks)</div>
<div class="">If so, either we need stable sorts, or a better ordering of incoming blocks, because the pointer equality we use will not definitely sort them into a consistent order</div>
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